First, I had been eyeing a mouthpiece for quite some time and nearly purchased a New Age Performance offering a couple of years ago when I was focused more on powerlifting. These are at the same $40 price point. My interest started with concerns in relation to damaging my teeth during training. I have a history of being a grinder and have had more than my fair share of dental work.
Second, my training is in serious need of a kickstart and sometimes a new toy is just the ticket. I have been struggling lately to get my breathing under control and get organized when getting back on the barbell during wods. I do not have any delusion that the advertised increased airway width of 9% will happen or if it will affect my breathing at all, but sometimes, just having another focus will allow me to push past a plateau.
Finally, I want a new toy. I am not ready to invest any more money in golf, scuba or bicycling and want for nothing in the crossfit space. I am not buying any new clothes or shoes. That unfortunately leaves one off gadgets like this.
Amanda Dvorak actually has a nice write up on the topic. It is featured on powerliftingtechnique.com